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Biomedical subjects

A J Clark

Publications and source records attributed to A J Clark.

At least 253 records · Page 14Linked to original sources
PubMed1986

Sodium and potassium intake measurements: dietary methodology problems.

This study compared methods that measured dietary intake of sodium and potassium by chemical analysis, by calculation from a table, and by measurement of these elements in 24-h urine. Total sodium included analyzed plus discretionary sodium. Analyzed elements were measured values in diets and urine performed by atomic absorption spectrophotometry. Calculated elements were estimated values from a food composition table. Food samples were collected by duplicate analysis. Total, analyzed, calculated, and discretionary sodium intake for 7 days by adolescent females averaged 2.890, 2.518, 1.852, and 0.372 g/day, respectively. Analyzed and calculated potassium intake by subjects averaged 1.447 and 1.667 g/day, respectively. Urinary sodium and potassium averaged 2.389 and 1.118 g/day, respectively. Subjects differed significantly in the amount of sodium ingested, partly due to discretionary sodium use. Total sodium and analyzed potassium were the accurate methods of determining sodium and potassium intake. Element intakes can be estimated from regression equations.

Adolescent↗
PubMed1986

Fat in the diets of adolescent girls with emphasis on isomeric fatty acids.

To determine the amount of isomeric fatty acids in the diets of a segment of the American population, daily food intake was collected, using the duplicate portion method, from eight healthy white adolescent girls for 7 days. The fifty-six diets were analyzed for fatty acids by gas-liquid chromatography. The amount of trans isomers of octadecenoic acid (18:1t) in the diets of the eight girls ranged from 3.5 to 8.2% of total fatty acids with an average of 5.3%. Other trans fatty acids included trans isomers of 14:1 and 16:1, and cis,trans and trans,cis isomers of 18:2. No measurable amounts of trans,trans octadecadienoic acid (18:2tt) were found in the diets of the girls. The total trans fatty acid content of the diets averaged 6.5% of total fatty acids. The daily consumption of total trans fatty acids by the eight girls over a 1 wk period averaged 3.1 g, with 2.6 g of this being 18:1t.

Adolescent↗
PubMed1986

Synthesis of linear plasmid multimers in Escherichia coli K-12.

Linear plasmid multimers were identified in extracts of recB21 recC22 strains containing derivatives of the ColE1-type plasmids pACYC184 and pBR322. A mutation in sbcB increases the proportion of plasmid DNA as linear multimers. A model to explain this is based on proposed roles of RecBC enzyme and SbcB enzyme (DNA exonuclease I) in preventing two types of rolling-circle DNA synthesis. Support for this hypothesis was obtained by derepressing synthesis of an inhibitor of RecBC enzyme and observing a difference in control of linear multimer synthesis and monomer circle replication. Reinitiation of rolling-circle DNA synthesis was proposed to occur by recA+-dependent and recA+-independent recombination events involving linear multimers. The presence of linear plasmid multimers in recB and recC mutants sheds new light on plasmid recombination frequencies in various mutant strains.

DNA, Bacterial↗
PubMed1986

Factors related to blood pressure in a biracial adolescent female population.

Blood pressure levels, anthropometric parameters, and dietary intakes were assessed in 1981 and 1983 in a population of black (n = 236) and white (n = 296) adolescent girls, aged 14 and 16 years in 1983. The 14-year-old black girls exhibited significantly higher mean systolic and diastolic blood pressures than whites in both years. Body weight and Quetelet index were more strongly associated with blood pressure than were height and triceps skinfold thickness. Correcting blood pressures for weight, Quetelet index, 2-year changes in height, and age at menarche decreased in each case (but did not negate) the observed race differences in blood pressure. Dietary calcium and potassium intakes were inversely related to blood pressure, and a race difference in the intake of these nutrients (whites greater than blacks) was observed. Covariate adjustment for calcium, but not for potassium, decreased the magnitude of race differences in blood pressure. Family type (single-parent vs nuclear) and place of residence (urban vs nonurban) appeared to be the most important confounding variables for race differences in blood pressure, since differences largely were eliminated by controlling for these factors. Conflicting reports in the literature regarding the age range during which race differences in blood pressure become apparent may be partially attributed to the complex interrelationships among these factors and the potential influence of other genetic-environmental interactions that may also play a role in blood pressure regulation.

Adolescent↗
PubMed1986

Influence of dietary calcium on bone calcium utilization.

In Experiment 1, 10 microCi 45Ca/day were administered to 125 hens for 10 days. Hens were then allocated to five treatments with calcium levels ranging from .08 to 3.75% of the diet. In Experiment 2, hens with morning oviposition times were randomly allocated to 11 treatments that were periods of time postoviposition ranging from 6 hr to 24 hr, in 2-hr increments (Experiment 2). At the end of each 2-hr period, eggs from 25 hens were removed from the uterus. The 18-, 20-, and 22-hr treatments were replicated three times. In Experiment 3, hens were fed either ad libitum or feed was withheld the last 5 or 6 hr before oviposition. In Experiment 4, hens were fed 10 microCi of 45Ca for 15 days to label skeletal calcium. Hens were divided into two groups and fed a .08 or 3.75% calcium diet for 2 days. On the second day, 25 hens fed the 3.75% calcium diet were intubated with 7 g of the same diet containing .5 g calcium at 1700, 2100, 0100, 0500, and 0700 hr. The measurements used were egg weight, shell weight, and 45Ca content of the egg shell. Results indicated a significant linear or quadratic regression of dietary calcium levels on 45Ca accumulation in eggshells and eggshell weight (Experiment 1). As the calcium level of the diet increased, eggshell weight increased and 45Ca recovery decreased. Utilization of skeletal calcium for shell formation ranged from 28 to 96%. In Experiment 2, the rate of shell calcification was not constant throughout the calcification process but varied significantly.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Influence of time of calcium intake on bone and dietary calcium utilization.

Sixteen hens, 67 weeks old, having oviposition times at 0700 +/- .25 hr, were used in Experiment 1. Hens were randomly divided into two treatments and fed a .08% calcium diet following oviposition. For 5 days, at either 0800 (AM) or 1600 (PM) hours, hens received 3.65 g of calcium by intubation. On Day 1, the calcium source contained 25 microCi of calcium-45 (45Ca). Eggs and excreta were collected daily for 45Ca analysis. Experiment 2 was similar to Experiment 1 except that 34-week-old hens were used. Calcium-45 activity of the egg shell, excreta, serum, and total contents of the gastrointestinal (GI) tract was determined. Results of Experiments 1 and 2 indicated that hens receiving their daily supply of calcium in the PM deposited significantly more of that day's dietary calcium on the following day's egg than hens receiving calcium in the AM. Excreta from the AM-treated hens contained significantly more 45Ca than that from the PM-treated hens during the first 24 hr in both experiments. In Experiment 2, the quantity of 45Ca in serum and GI tract contents was significantly higher from hens in the PM treatment. It was concluded that hens utilized significantly more calcium for egg shell formation from PM consumption rather than AM consumption and, therefore, were less dependent on bone reserves when the calcium was consumed in the PM.

Animals↗
PubMed1986

An approach to analyzing UV mutagenesis in E. coli.

UV mutagenesis of single-strand DNA phage can be divided into three types: induced untargeted; induced targeted; and uninduced targeted. We report the development of new tools to determine the number of processes which contribute to these types of mutagenesis. An E. coli tRNA gene, glyU, has been cloned using M13 derivatives mp8 and mp9 as vectors. The nucleotide sequence of glyU and its flanking regions is presented. In this paper, phage glyU anticodon mutants are detected by their ability to suppress GAA and GAT missense mutations in trpA. We used phage carrying GAG and CTC at the anticodon position and found results consistent with the hypothesis that two processes act to produce the transition to GAA suppression: an uninduced regionally targeted process; and an induced locally targeted process with some untargeted activity. The transversion frequency to GAT suppression on the other hand responded as if only an uninduced locally targeted process was involved. Thus, we hypothesize that the new tools have discriminated three different processes of mutagenesis and we discuss further work designed to test this hypothesis.

Anticodon↗
PubMed1986

Use of published analyses of food items to determine dietary trans octadecenoic acid.

To estimate the dietary levels of trans octadecenoic acid (18:1t) in the diets of eight healthy white adolescent girls, diet records were obtained for a 7-day period. Published trans fatty acid values in foods were used to calculate the trans octadecenoic acid present in the diets. The usefulness of this method was tested by comparing the estimated values with values obtained by chemical analysis of diets collected by the duplicate portion technique from the same subjects over the same period of time. There was no significant difference in the values for the trans octadecenoic acid content of the 54 diets used in this study whether the values were calculated from the diet records or determined by chemical analysis. Dietary trans octadecenoic acid averaged 5.3% of total fatty acids by both methods. The mean trans octadecenoic acid in the daily diet was 2.8 gm as calculated from the diet records and 2.6 gm according to actual analysis. Those values were not significantly different. The present study demonstrated that the trans octadecenoic acid content of the diets of a group of adolescent girls can be estimated from diet records using previously published values for individual food items.

Adolescent↗
PubMed1986

Nutrients supplied by food groups in diets of teenaged girls.

Sources of nutrients were determined in diets of teenaged girls, a group generally thought to be at nutritional risk. This study of Southern adolescent girls of two races examines intakes of energy, energy-yielding nutrients, vitamins, minerals, and other components of various food groups. Effects of race, age, place of residence, and per capita income on nutrients furnished by food groups were determined from two 24-hour dietary recalls from each of 1,195 girls, aged 12, 14, or 16. Of the food groups examined, foods of low nutrient density provided the most energy, fat, and carbohydrate. The meat group provided the most protein. Dairy products, which supplied the largest amounts of six vitamins and minerals of any food group, were used less by black, rural, or older teenagers than by white, urban, or younger girls. Blacks obtained more vitamin A from vegetables and more thiamin from meat than whites. Amounts of meat, starchy, and low-nutrient-density subgroups also varied with race, age, and/or place of residence. As income increased, consumption of starches (especially breakfast cereals) and eggs decreased and that of fruit increased.

Adolescent↗
PubMed1985

Sequence structures of a mouse major urinary protein gene and pseudogene compared.

Laboratory mouse strains carry approximately 35 major urinary protein (MUP) genes per haploid genome, tightly clustered together on chromosome 4. Most belong to two main groups (Groups 1 and 2). The available evidence strongly suggests that the Group 1 genes are active while the Group 2 genes are pseudogenes. Here we present the complete sequence of a Group 1 gene and a Group 2 gene and 700 bp of flanking sequence. The sequence of the Group 1 gene is consistent with its being active. The Group 2 gene contains two stop codons and a frame-shift mutation in the reading frame defined by the Group 1 gene, and would code for a signal peptide 25 rather than 19 amino acids long. The Group 2 gene differs from the Group 1 gene in other ways: a deletion upstream of the TATA box and another in intron 3, a base change in the TATA box itself, a 2 bp duplication at the splice acceptor boundary of intron 6, an altered poly(A) addition signal and a 1-base deletion 5' to the initiation codon. Some of these differences may explain the 10- to 20-fold higher level of Group 1 mRNA in mouse liver, and the fact that Group 1 and Group 2 transcripts are mainly spliced differently. The presence of the stop codon means that the Group 2 gene is a pseudogene in the context of the Group 1 gene. However, there is some evidence that the mature hexapeptide that it would code for may have biological activity. The 12 acceptor splice sites of the two genes all contain the identical sequence ACAG at the exon boundary.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Analysis of mouse major urinary protein genes: variation between the exonic sequences of group 1 genes and a comparison with an active gene out with group 1 both suggest that gene conversion has occurred between MUP genes.

Here we compare the exonic sequences of four Group 1 mouse major urinary protein (MUP) genes and four Group 1 cDNA sequences. These define seven different nucleotide sequences which differ from each other by 0.35% of bases on average, and which would code for seven different MUP proteins that could probably be resolved physically into at least five classes. The sequences differ at 13 nucleotide positions and at six codons, and although they are closely related their descent cannot be described by a simple series of duplications. We also describe the sequence of another liver cDNA (pMUP15) which has diverged from the Group 1 consensus sequence in 14.6% of bases. The divergence is much greater over exons 1-3 than over exons 4-6, suggesting that an ancestral gene conversion event has occurred. pMUP15 also differs from the Group 1 genes in having a longer signal peptide sequence and a different splice configuration between exons 6 and 7. Unlike the Group 1 sequences, pMUP15 contains a potential N-linked glycosylation site. Other published work has shown that a shorter cDNA clone which is identical over their common sequence to pMUP15 codes for MUP proteins that are unusually large in size and acidic in pI. We show here that mouse urine does indeed contain a glycosylated MUP protein with those properties, presumably the product of the gene that corresponds to pMUP15.

Animals↗
PubMed1985

Evolutionary amplification of a pseudogene.

The family of mouse major urinary protein (MUP) genes has about 35 members, clustered together on chromosome 4. Most of the genes belong to two major subfamilies (group 1 and group 2) each with 12-15 members. Recently we showed that most of the group 1 and group 2 genes are arranged in pairs, each containing a group 1 and a group 2 gene in divergent transcriptional orientation, with 15 kilobases of DNA between the two cap sites. Here we present the nucleotide sequence of the first exon of six group 1 genes and four group 2 genes. The data confirm the close relationship of the genes within each group and the considerable divergence of the two groups from each other. The four group 2 genes all carry the same nonsense mutation in codon 7 of the sequence that specifies the mature protein. Thus, not only do these genes have a common ancestor, but also it seems that their amplification followed the mutation of the ancestor to a pseudogene. Taking into account the 3' flanking regions of the two genes, the overall size of each gene-pair is about 45 kilobases. The sequencing data supports our earlier suggestion that this 45 kilobase domain is the unit of Mup amplification.

Animals↗
PubMed1985

Epidermal growth factor regulates the expression of its own receptor.

The epidermal growth factor (EGF) receptor gene is the cellular homolog of the avian erythroblastosis virus erbB oncogene. Control of EGF receptor expression determines cellular responsiveness to EGF and might play an important role in neoplastic development. Using RNA blot hybridization, we have found that exposure of human KB carcinoma cells to EGF results in elevated levels of EGF receptor mRNA. The phorbol ester 4 beta-phorbol 12-myristate 13-acetate also stimulates EGF receptor RNA accumulation. Immunoprecipitation of metabolically labeled (30 min) EGF receptor protein revealed that synthesis of new EGF receptor follows the increase in receptor RNA. Addition of cycloheximide together with EGF further enhances EGF receptor RNA accumulation. Results of nuclear runoff-transcription experiments suggest that the stimulatory effects of EGF and cycloheximide are most likely due to a posttranscriptional control mechanism.

Cells, Cultured↗
PubMed1985

Cloning of the Escherichia coli recJ chromosomal region and identification of its encoded proteins.

A 9.6-kilobase BamHI-SalI fragment carrying recJ+ was cloned into vector pBR322. Deletion and transposon mutagenesis were used to map the recJ gene on this fragment. The maxicell protein-labeling technique was used to correlate a functional recJ gene with the presence of a polypeptide of 53,000 apparent molecular weight. Two additional genes, one encoding two proteins of 26,000 and 25,000 Mr and the other encoding a 31,000-Mr protein, were mapped on a 3.7-kilobase HindIII-SalI subfragment with recJ. Functions for these adjacent genes are not known; however, insertion mutations in these genes lessen the expression of the putative recJ protein detected in maxicells. A 9.6-kilobase BamHI-SalI fragment carrying the temperature-sensitive mutation recJ147 was also cloned and used for complementation studies to identify other recJ mutations.

Bacterial Proteins↗
PubMed1985

Mutation-dependent suppression of recB21 recC22 by a region cloned from the Rac prophage of Escherichia coli K-12.

Using pBR322 as a vector, we cloned a 5.95-kilobase fragment of the Rac prophage together with 1.70 kilobases of a flanking Escherichia coli chromosome sequence. The resulting plasmid (pRAC1) was unable to suppress the mitomycin and UV sensitivity and recombination deficiency of a recB21 recC22 strain. Five spontaneous mitomycin-resistant derivatives contained deletion mutant plasmids. These plasmids also suppressed the UV sensitivity and recombination deficiency of their recB21 recC22 hosts. All five deletions were contained within a 2.45-kilobase EcoRI-to-HindIII segment of the plasmid. By substituting the corresponding 2.45-kilobase EcoRI-toHindIII fragments of Rac prophage isolated from sbcA+, sbcA6, and sbcA23 strains for the shortened segment of one of the deletion mutant plasmids, we were able to show that sbcA mutations map in this region. Also in this region is the site (or closely linked sites) at which previous studies had shown that insertion of Tn5 and IS50 leads to suppression of recB21 recC22. The sequence in this region that must be altered or circumvented to allow suppression is discussed. Also presented are data correlating the expression of nuclease activity with the degree of suppression.

Bacteriophage lambda↗
PubMed1985

The 45-kb unit of major urinary protein gene organization is a gigantic imperfect palindrome.

The multigene family which codes for the mouse major urinary proteins consists of about 35 genes. Most of these are members of two distinct groups, group 1 and group 2. The group 1 and group 2 genes are organized in head-to-head pairs within 12 to 15 remarkably uniform chromosomal units or domains about 45 kilobase pairs (kb) in size. The 45-kb units are located on chromosome 4, and many of them are adjacent to each other. We propose that the 45-kb unit is a unit both of organization and of evolutionary change. In this study the homologies within the unit were observed by examining, in an electron microscope, heteroduplex and foldback structures made from cloned major urinary protein genes. These show that the 45-kb unit is a gigantic imperfect palindrome. Each arm of the palindrome contains two regions of inverted symmetry of 9.5 and 4.5 kb separated by a 3-kb nonsymmetrical region. We argue that the nonsymmetrical regions arose by a series of deletion events in the two arms of the palindrome. The center of the 45-kb unit is an 8-kb sequence without inverted symmetry flanked by the 9.5-kb regions, which contain the 4-kb genes and their immediate 5' and 3' flanking regions. The junction between adjacent 45-kb units is a 2- to 4-kb sequence without inverted symmetry flanked by the 4.5-kb regions. Some of the 45-kb units are arranged as direct tandem repeats. Others appear to be in inverted orientation with respect to a neighboring unit. Cloned major urinary protein genes show few incidences of the repetitive elements B1, B2, R, and MIF. Two elements, a B1 and an R, may be a constant feature of the 45-kb units. If so, in those cases in which the units are in tandem array, both of these elements will occur with a 45-kb periodicity. A comparison of corresponding parts of different 45-kb units shows that they differ because of a number of deletion or insertion events, particularly in the regions 3' to the genes.

Animals↗
PubMed1985

Structure and localization of genes encoding aberrant and normal epidermal growth factor receptor RNAs from A431 human carcinoma cells.

A431 cells have an amplification of the epidermal growth factor (EGF) receptor gene, the cellular homolog of the v-erb B oncogene, and overproduce an aberrant 2.9-kilobase RNA that encodes a portion of the EGF receptor. A cDNA (pE15) for the aberrant RNA was cloned, sequenced, and used to analyze genomic DNA blots from A431 and normal cells. These data indicate that the aberrant RNA is created by a gene rearrangement within chromosome 7, resulting in a fusion of the 5' portion of the EGF receptor gene to an unidentified region of genomic DNA. The unidentified sequences are amplified to about the same degree (20- to 30-fold) as the EGF receptor sequences. In situ hybridization to chromosomes from normal cells and A431 cells show that both the EGF receptor gene and the unidentified DNA are localized to the p14-p12 region of chromosome 7. By using cDNA fragments to probe DNA blots from mouse-A431 somatic cell hybrids, the rearranged receptor gene was shown to be associated with translocation chromosome M4.

Amino Acid Sequence↗